Their word is their bond, and they do what they say — even if the “word” on one side is a loud trill and grunt, and, on the other, the excited twitterings of a bird.

Researchers have long known that among certain traditional cultures of Africa, people forage for wild honey with the help of honeyguides — woodpecker-like birds that show tribesmen where the best beehives are hidden, high up in trees. In return for revealing the location of natural honey pots, the birds are rewarded with the leftover beeswax, which they eagerly devour.

Now scientists have determined that humans and their honeyguides communicate with each other through an extraordinary exchange of sounds and gestures, which are used only for honey hunting and serve to convey enthusiasm, trustworthiness and a commitment to the dangerous business of separating bees from their hives.

The findings cast fresh light on one of only a few known examples of cooperation between humans and free-living wild animals, a partnership that may well predate the love affair between people and their domesticated dogs by hundreds of thousands of years.

Claire N. Spottiswoode, a behavioral ecologist at Cambridge University, and her colleagues reported in the journal Science that honeyguides advertise their scout readiness to the Yao people of northern Mozambique by flying up close while emitting a loud chattering cry.

For their part, the Yao seek to recruit and retain honeyguides with a distinctive vocalization, a firmly trilled “brrr” followed by a grunted “hmm.” In a series of careful experiments, the researchers then showed that honeyguides take the meaning of the familiar ahoy seriously.

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Orlando Yassene harvesting honeycombs from a wild bees’ nest in the Niassa National Reserve in Mozambique.CreditClaire Spottiswoode

The birds were twice as likely to offer sustained help to Yao foragers who walked along while playing recordings of the proper brrr-hmm signal than they were to participants with recordings of normal Yao words or the sounds of other animals.

“The fact that the honeyguides were responding more to the specialized sound implies they recognize the specific information content in the signal,” Dr. Spottiswoode said. “It’s not simply a cue to human presence. It’s a signal that the person will be a good collaborator.”

John N. Thompson, a distinguished professor of ecology and evolutionary biology at the University of California, Santa Cruz, said: “I think it’s an absolutely terrific paper. This is one of those ‘just-so’ natural history stories we’ve known for years, and now we’ve got some hard-won data to show it really is so.”

The report describes in detail the trans-species collusion to enjoy the fruits of bee labor. Bees transform gathered nectar and pollen into honey for food and wax for honeycomb housing. As honey is among the most energy-rich foods in nature, it is not surprising that bees guard it with their lives.

African bees are particularly aggressive and will swarm any intruder that so much as jiggles an adjoining branch. Even our closest relatives are loath to disturb a beehive.

“Chimpanzees want to eat honey at least as much as humans do,” Brian M. Wood, a biological anthropologist at Yale University, said. “But they don’t possess the technologies that have allowed us to tap into that resource.”

The Yao know what to do to subdue bee defenses. They wedge a bundle of dry wood wrapped in palm fronds onto a long pole, set the bundle on fire, hoist it up and rest it against a beehive in a tree. When most of the bees have been smoked out, the Yao chop down the tree, tolerate the stings of any bees that remain and scoop out the liquid gold within.

Much harder for the Yao is finding the hives. That’s where the honeyguides come in. Not only can they easily flit from tree to towering tree; they have unusually large olfactory bulbs, and they are good at smelling wax, which makes up a good part of their diet.

“It’s decidedly odd to eat wax, but if you’ve got the metabolism to break it down, it’s a good source of calories,” Dr. Spottiswoode said.

The birds can nibble on waxy plants, waxy insects, the waxy detritus in an abandoned bee nest. Or they can summon human honey hunters to crack open a felled and toasted hive, remove the honey and leave the fresh waxy infrastructure to them.

The birds can recruit helpers with a chatter, or be recruited with a trill-grunt. They can show their human companions the right trees with more chatters or a flick of their white-tipped tails. When assisted by honeyguides, Yao hunters found beehives 54 percent of the time, compared with just 17 percent when unaided.

Researchers have identified a couple of other examples of human-wild animal cooperation: fishermen in Brazil who work with bottlenose dolphins to maximize the number of mullets swept into nets or snatched up by dolphin mouths, and orcas that helped whalers finish off harpooned baleen giants by pulling down the cables and drowning the whales, all for the reward from the humans of a massive whale tongue.

But for the clarity of reciprocity, nothing can match the relationship between honeyguide and honey hunter. “Honeyguides provide the information and get the wax,” Dr. Spottiswoode said. “Humans provide the skills and get the honey.”

How the alliance began remains mysterious, but it is thought to be quite ancient.

“It appears to depend on humans using fire and hand-axes,” Richard Wrangham, a biological anthropologist at Harvard University, said. Those talents date back to the lower Paleolithic, “so the relationship could be more than a million years old.”

The bird might even have played a role in the emergence of fully modern humans and their energetically demanding brains. Honey is a vital resource for many subsistence cultures, Dr. Wrangham said, “sometimes supplying 80 percent of calories in a month.”

It is beloved by all who depend on it. Among the Hadza of Tanzania, Dr. Wood said, “it’s the top choice of what people claim they would like to eat — the sweet, delicious meal they’ll go for when given the chance.”

A version of this article appears in print on , on Page A6 of the New York edition with the headline: African Tribesmen Can Talk Birds Into Helping Them Find Honey. Order Reprints | Today’s Paper | Subscribe